Cats, which are among the most popular types of domestic pets, are usually trained to use a litter box for elimination of both liquid and solid wastes. A cat litter box is normally made of plastic or like material so that a cat's urine will not leak through the box. Other types of cat litter box have been proposed, as in the construction described in Rockaitis U.S. Pat. No. 5,249,549, in which the litter box is made of a material that absorbs liquid but does not permit it to leach through to the exterior of the box. The litter used in boxes of this kind may be one of any number of particulate litter materials that absorb moisture from the waste of the cat and that may also suppress odor from cat wastes. Some forms of cat litter form clumps when wet. Usually, a cat will bury its solid waste in the litter material in the box.
Most cat owners take appropriate action to discard the litter from a cat litter box after an appreciable period of time, often several days. On the other hand, even before the litter has been thoroughly saturated with wastes from the cat or cats that use it, a cat may be inclined to push some of the litter out of the box, particularly if the odor is strong. In any event, the person using a cat litter box, usually the owner of the cat or cats, may find the task of emptying the cat litter to be personally obnoxious. Thus, a number of prior art devices have been proposed for cleaning cat litter boxes; devices of this kind are disclosed in U.S. Pat. No. 4,096,827, No. 4,117,804, No. 4,190,525, No. 4,325,325, No. 4,325,822, and No. 5,226,388. Perhaps the best of these devices is disclosed in Carlisi U.S. Pat. No. 5,048,465.
The self-cleaning cat litter box disclosed in the Carlisi patent utilizes a rake or comb that is normally maintained in a storage position at one end of the litter chamber. This comb is moved through the litter, periodically, from the rake storage end of the chamber to the opposite end, which constitutes a discharge end for the chamber. At the discharge end of the chamber the rake moves up out of the litter and discharges any clumps collected by the comb into a disposal receptacle. The present invention provides effective improvement for the rake drive of the Carlisi device so that movement of the comb or rake through the litter can be made responsive to entry and exit of the cat from the litter box. Cats are no more constant in their elimination habits than human beings; periodic cleaning may be inappropriate. The invention also provides for improvements in the disposal receptacle, which may also serve as a container for a new litter supply. Alarms are also provided for an insufficient litter supply and a full disposal receptacle.